The invention relates to the processing of digitized video signals and more particularly to a process for the code conversion of a video digital train of eight parallel bits and a device for transmitting digitized video signals using such a process.
In so-called digital television, video signals are transmitted in the form of a train of eight-bit words resulting from the two-state coding by non-return to zero (NRZ) of the video signal on 256 levels. Such signals can be processed as they are in a reception station, but in certain cases and in for example local distribution networks, they are transmitted in the form of a bit series sequence. When this retransmission is carried out by means of a coaxial cable, it is possible to use parallel-series conversion devices utilizing a code conversion process which employs a ternary code (three possible states for coding the two levels 1 and 0). They reduce the necessary band, but use a signal with three levels for easily reconstituting the timing of the bits. Such devices are difficultly realizable for transmission using optical cables because it is difficult to transmit three levels on such cables. However, there are fewer pass band limitations in the case of optical fibre devices.